The long term objectives of the project intend to characterize presently unknown signalling mechanisms that are used in mediating the neurogenic to gliogenic fate switch of neural stem cells (NSC) within the developing central nervous system (CNS). We have developed an in vitro culture system that recapitulates the events observed in vivo: NSC first enter a neurogenic phase and later switch to an astrogliogenic phase. We have discovered that media collected from cells after several days of culturing has astrogliogenic inducing and neurogenic inhibiting activity. We have hypothesized that as NSC reach the end of their neurogenic potential they secrete some type of factor that is able to promote astrogliogenesis and actively inhibit the neurogenic fate. We have ruled out the possibility that the collected media contains many of the known astrogliogenic inducing factors. Our future goals intend to characterize the biological function of the CM and decipher the exact times and cell ages during which it contains these astroglial inducing and neuronal non-inhibiting activities.